Sons perhaps should have taken the lead in the opening stages, with Michael Ruth in particular missing a close-range header, but failed to take advantage.
They were made to pay on 20 minutes when Russell Dingwall found room to poke the ball in off the post, ending the hosts run of five consecutive clean sheets.
The lead was doubled seven minutes later when Ross Draper headed into the net from a corner and Stevie Farrell’s side had it all to do.
They reduced the deficit before the interval when Ruth got his header right on this occasion after superb link-up play from Kalvin Orsi and Carlo Pignatiello on the right.
Much of the second period was played in Elgin’s half but Sons failed to seriously test Tom McHale.
Jay Hogarth was the busiest of the ‘keepers as he made two vital interventions to keep out one-on-one opportunities before Dumbarton got their break.
Ryan Blair’s attempt from the edge of the box fell kindly to sub James Graham who took a touch before finding the bottom corner.
Sons final league position in cinch League Two remains undetermined with one fixture to go as they head to Peterhead before the play-offs begin.